The Impact on Peer Mentorship After Implementation of a Competency-Based Residency Curriculum in Canadian Radiation Oncology Training Programs.

Purpose: Peer mentorship provides professional and personal support between physicians with similar experiences and levels of training. While peer mentorship has shown to benefit academic success and professional growth, little data has examined contextual factors, such as curricular change, that may affect the quality of these relationships. This study aims to explore the impact of a new, nationwide radiation oncology (RO) residency curriculum, known as competence by design (CBD), on peer mentorship experiences between Canadian RO residents. Methods and Materials: A qualitative study, with a social constructivist approach, was conducted with 2 groups of Canadian RO residents. The first were those in the academic year before CBD implementation (non-CBD cohort), and the second were those in the inaugural year of CBD (CBD cohort). Semistructured 1-on-1 interviews were conducted to explore experiences of peer mentorship as it related to curriculum change. Interviews were transcribed and analyzed with deductive and inductive methods until data saturation. Results: Between April and December 2021, 14 participants (6 non-CBD and 8 CBD residents) from 8 out of 10 eligible English-speaking RO training programs across Canada participated. Three major themes were identified: (1) the CBD cohort identified fewer opportunities for peer mentorship, with specific concerns regarding new evaluation processes and uncertainty about the later stages of training; (2) there was minimal impact on specialty-specific learning; and (3) peer mentorship thrived when occurring as spontaneous in-person interactions. Conclusions: Inaugural residents of a CBD curriculum perceived fewer opportunities for peer mentorship. There were specific concerns about new evaluative processes, though this did not affect specialty-specific learning. Peer mentorship was most impactful as informal and in-person interactions. Our findings suggest that unintended consequences of curriculum change may be mitigated by improving communication about new training objectives and increasing opportunities for informal interactions between residents.

Exploring the Future of Cancer Impact in Alberta: Projections and Trends 2020-2040.

The impact of cancer in Alberta is expected to grow considerably, largely driven by population growth and aging. The Future of Cancer Impact (FOCI) initiative offers an overview of the present state of cancer care in Alberta and highlights potential opportunities for research and innovation across the continuum. In this paper, we present a series of detailed projections and analyses regarding cancer epidemiological estimates in Alberta, Canada. Data on cancer incidence and mortality in Alberta (1998-2018) and limited-duration cancer prevalence in Alberta (2000-2019) were collected from the Alberta Cancer Registry. We used the Canproj package in the R software to project these epidemiological estimates up to the year 2040. To estimate the direct management costs, we ran a series of microsimulations using the OncoSim All Cancers Model. Our findings indicate that from 2020, the total number of annual new cancer cases and cancer-related deaths are projected to increase by 56% and 49% by 2040, respectively. From 2019, the five-year prevalence of all cancers in Alberta is projected to increase by 86% by 2040. In line with these trends, the overall direct cost of cancer management is estimated to increase by 53% in 2040. These estimates and projections are integral to future strategic planning and investment.

Supply and Demand for Radiation Oncologists in Canada: Workforce Planning Projections From 2020 to 2040.

PURPOSE: The number of Canadians diagnosed with cancer, and subsequent demand for radiation therapy, are expected to increase over time. This study aimed to update our needs-based workforce planning model to ensure appropriate staffing levels in the future. METHODS AND MATERIALS: The supply of radiation oncologists, by age group, sex, and full-time equivalent status, was projected from 2020 to 2040 using a recursive-aging, input-output model developed with seeding parameters derived from national sources. The demand for radiation oncologists until 2040 was estimated using referral patterns for radiation therapy and consultation workload metrics applied to projected annual cancer incident cases to calculate required full-time equivalent positions. Baseline model parameters were also applied to the 2005-2019 workforce and incident case data to evaluate preprojection supply and demand trends. RESULTS: Preprojection trends for 2005 to 2019 revealed accelerated staffing growth that transitioned from a workforce shortage to a surplus state in 2014 followed by substantial growth slowdown in 2016. The model predicts a transient surplus of radiation oncologists until 2026 followed by a projected deficit in subsequent years. Sensitivity analyses using the plausible range for each parameter continued to favor an undersupply, suggesting a trainee shortage unable to meet workforce expansion needs. Considering possible future declining trends in radiotherapy utilization and workload, calculations to inform corrective efforts in resident numbers resulted in 25 entry positions per year, up from 21 per year currently. Geographic distribution of trainees, relative to workforce and cancer incidence distributions, could be improved with more residency positions in Canadian regions outside Ontario. CONCLUSIONS: Demand for radiation therapy and radiation oncologists in Canada are expected to grow more quickly than future expansion in staffing levels. Our workforce planning model provides evidence for more trainee requirements to inform stakeholders of possible corrective actions to training programs and recruitment. Further research is needed to explore additional strategies to expand capacity and high-quality delivery of radiation therapy to meet the foreseeable increase in Canadian patients with cancer.

Representation of Women in Canadian Radiation Oncology Trainees and Radiation Oncologists: Progress or Regress?

Purpose: The study objective was to determine the representation of women in Canadian radiation oncology (RO) trainees and the radiation oncologist workforce over time. Methods and Materials: Gender data for Canadian RO trainees (residents and fellows) and radiation oncologists were collected from the Canadian Post-MD Education Registry (1994-2021) and Canadian Medical Association (1994-2019). Visa trainees were excluded. Gender parity was defined as a 1:1 female-to-male ratio. Descriptive statistics were used to summarize the data. Results: Female trainee proportions varied with 2 rising trend periods (1994-1998: 38%-43%, P = .93; 2002-2014: 35%-51%, P = .53) and 2 regression trend periods (1998-2002: 43%-35%, P = .83; 2014-2021: 52%-35%, P = .011). Gender parity was observed in RO trainees between 2012 and 2016. The annual number of RO trainees ranged from 66 to 173 with 2 near-parallel periods of gender-associated growth (1994-1996; 2002-2008) and regression (1997-2001; 2009-2016) followed by gender divergence (2017-2021) with increasing male and decreasing female trainees. Nearly all Canadian regions, except Ontario, reached 50% or higher female representation in RO trainees during the study period. In the radiation oncologist workforce, female representation increased from 20% (54/271) to 37% (217/582) between 1994 and 2019, and all regions and age groups demonstrated higher female representation over time. Within radiation oncologist subgroups, age <35 years old and Quebec region cohorts reached gender parity. Conclusions: Representation of women varied in Canadian RO trainees and has fallen since 2014, whereas female representation generally increased in the radiation oncologist workforce over time. Gender parity was observed in RO trainees, radiation oncologists <35 years old, and radiation oncologists in Quebec. Recent declining female representation among RO trainees is worrisome, and further study is warranted to identify potential gender-based barriers in attracting women to the specialty.

Employment Outcomes for Canadian Radiation Oncology Graduates: 2020 Assessment and Longitudinal Trends.

Purpose: Canadian radiation oncology (RO) trainees have experienced employment challenges after residency training. The present study was conducted to evaluate current employment trends and perform comparisons to prior reported assessments. Methods and Materials: A survey was administered to all 13 Canadian RO program directors requesting the employment status and location of their graduates during the past 3 years, and their perceptions on graduates' employment challenges. Visa trainees were excluded. Findings were compared with surveys performed in 2014, 2016, and 2018. Results: The response rate from RO program directors was 100%. There were 77 graduates identified who completed their residency training between 2017 and 2020. All had known employment status and location. Two (17%) 2020 graduates, 16 (84%) 2019 graduates, 17 (81%) 2018 graduates, and 24 (100%) 2017 graduates had staff employment. Of the 59 graduates with staff positions, 86% were in Canada. Some graduates (28%) obtained staff or locum employment in a province other than their training program. The proportion of graduates obtaining staff positions 1 year after residency increased to 84% from 46%-48% in prior assessments. Most program directors (62%) did not perceive any difficulties with their graduates finding staff employment or trainees transferring to training programs in other disciplines owing to perceived workforce challenges. Conclusions: Compared with 3 prior employment outcome assessments, this study observed a higher proportion of graduates with staff positions in Canada, fewer total graduates, fewer graduates seeking staff employment or in fellowship positions, and a trend for fewer graduates seeking employment or fellowships abroad. These findings support the view that the Canadian RO job market continues to improve. Although employment challenges for newly certified, Canadian-trained radiation oncologists still exist, national corrective measures to regulate resident intake in 2011 appear to have had a positive effect on the employment outcomes of recent Canadian RO graduates.

Clinical Learning, Didactic Education, and Research Experiences of Radiation Oncology Resident Physicians in Canada.

Changes in the field of radiation oncology (RO) impacts residency training. Assessing trainee experiences is essential to inform curriculum development. We aim to explore gaps and strengths in current Canadian RO training, as we move towards competency-based medical education (CBME). An online survey was distributed to residents at all Canadian RO training programs. Surveys consisted of 66 open-ended, Likert-scale, matrix-style, and multiple-choice questions, and assessed clinical exposure, didactic teaching, professional relationships, and research experiences. Statistics were calculated from anonymized, aggregate responses. Out of 128 eligible residents, 53 responded (41% response rate). Of these, 57% were male, and 77% were Canadian medical graduates. Senior residents (PGY-4 to PGY-5) perceived insufficient exposure to lymphoma and ocular malignancies, brachytherapy for breast and esophagus malignancies, and stereotactic radiotherapy of the pancreas, prostate, and adrenal gland. Half (51%) had training on image-guided radiotherapy (IGRT) challenges, and 43% had a formal staff mentor. Most residents presented at least one research project at conferences (77%) and authored ≥ 1 publications (66%) during residency. Canadian RO residents are satisfied with their clinical training and educational experience in high-volume tumor sites and high-volume brachytherapy procedures. Areas identified for potential improvement are (1) low-volume tumor sites; (2) low-volume brachytherapy procedures; (3) low-volume stereotactic radiotherapy sites; (4) IGRT challenges; and (5) mentorship opportunities. These findings will inform future CBME curriculum revisions.

Motivations, Well-Being, and Career Aspirations of Radiation Oncology Resident Physicians in Canada.

Prior Pan-Canadian surveys of Radiation Oncology (RO) residents reveal a decrease in Canadian RO employment opportunities. Canadian RO resident levels increased from 130 in 2003, peaked at 209 in 2009, then decreased to 130 in 2017. Recognizing that RO has entered another period of transition, we re-examined resident motivations and perspectives on the job market and explored well-being and career aspirations among a contemporary cohort of Canadian RO residents. An online survey was distributed to residents at all Canadian RO training programs. Surveys consisted of 75 open-ended, Likert-scale, matrix-style, and multiple-choice questions. Student's t test compared subgroups, with statistical significance at p ≤ 0.05. Out of 128 eligible residents, 84 completed the survey (66% response rate) with representative sampling from each training year. Demographics reveal 53% male, and 85% Canadian registry-funded. Top training-related stressors were exam performance, job prospects, and physical/psychological demands of residency. Most intend to pursue fellowship post-residency (80%) and practice in Canada (88%). Few believe they can obtain staff positions treating preferred tumor sites (38%) or at preferred geographic locations (28%). Residents view job market being less competitive than 5 years ago (40%) and predict it will be less competitive in 5 years (60%). Canadian RO residents feel adequately trained, and most pursue post-residency fellowships. Current perceptions of the Canadian job market remain guarded, but appear more optimistic about the future. This update provides insights into current RO training and identifies areas that could be addressed by incoming competency-based medical education models for RO.

The Role of Coaches within Academic Medical Departments: Is There Value to Integrating This into Academic Mentorship Programs?

This study evaluated the benefits of formal coaching within a mentorship program in a Canadian academic medical department. Between April 2016 and September 2018, an executive coach was made available to members of the Department of Oncology at the University of Calgary. Thirty-seven individuals sought and received formal coaching during this period, using up an average of four hourly sessions; of these individuals, 13% (20/150) are full-time faculty. Issues that facilitated interest in coaching included the following: needing to develop an individual life plan, wanting to improve work-life balance/time management and seeking advice about promotion or job application. This study found that coaching enabled participants to address their concerns 70% of the time and describes the elements of a coaching function within academic medical departments. We strongly recommend that academic departments provide opportunities for interested individual academics to receive coaching.

Institutional review of glial tumors treated with chemotherapy: the first description of PCV-related pseudoprogression.

BACKGROUND: Pseudoprogression refers to areas of enhancement on MRI postadjuvant chemoradiation that arise as a result of treatment-related effects. Pseudoprogression has been well described with temozolomide-based chemoradiation but has not been studied in the setting of procarbazine, lomustine, and vincristine (PCV) chemotherapy. We reviewed patients treated with PCV to investigate the occurrence of pseudoprogression. METHODS: Adults diagnosed with World Health Organization grade II or III gliomas between 2010 and 2015 and treated with PCV or temozolomide were identified. Patient, tumor, treatment, and MRI data were retrospectively collected and analyzed. Pseudoprogression was defined as new enhancement seen on MRI within 6 months of completion of adjuvant radiotherapy or concurrent chemoradiation, which improved or remained stable on subsequent scans without therapeutic intervention. If MRI showed areas of new enhancement outside the 6-month post-treatment window, which resolved or remained stable without treatment, or in patients who did not receive adjuvant treatment, it was referred to as "atypical pseudoprogression." RESULTS: Fifty-seven patients were identified. Nine (16%) patients were identified as having pseudoprogression on MRI. Two (4%) of these patients were treated with PCV and 7 (12%) were treated with temozolomide. Seventeen (30%) patients had atypical pseudoprogression: 8 (14%) treated with temozolomide, 8 (14%) treated with PCV, and 1 (2%) treated with both types of chemotherapy. CONCLUSIONS: We describe the first 2 cases of PCV-related pseudoprogression and 17 cases of atypical pseudoprogression. As the re-emergence of adjuvant PCV occurs in clinical practice, the occurrence of classical and atypical pseudoprogression could have a significant impact on clinical decision making.

Transition to practice in radiation oncology: Mind the gap.

INTRODUCTION: Physicians entering independent practice often express apprehension in managing the non-clinical aspects of practice. This study examined the perceived preparedness of radiation oncology (RO) residents for independent practice, identified education gaps, and discussed how these deficiencies could be addressed. MATERIALS AND METHODS: Focus groups with senior RO residents, fellows, new-to-practice radiation oncologists (ROs), and residency program directors were conducted. Data were coded using the Canadian Medical Education Directives for Specialists (CanMEDS) competencies using thematic analysis. RESULTS: Commonly reported gaps in the transition to practice (TtP) for ROs were lack of experience with: practice management, understanding the structure and function of the health care system and how it varies by jurisdiction, financial planning, effective communication and collaboration with other health care team members, creation of accurate and timely documentation, and radiotherapy problem-solving related to treatment planning and evaluation. Suggestions to address these challenges included use of mentorship, educational resources, courses, simulation-based medical education, improved graded responsibility, resident longitudinal clinics, and formal curricula in radiation therapy planning and evaluation. CONCLUSION: There are gaps in TtP education for RO trainees with opportunities for enrichment through the forthcoming implementation of a competency-based medical education framework in 2019. The gap in perceived competency in physician-related radiotherapy tasks may be caused by the complex interaction of clinical workflow processes, people and technology that has led to ineffective integration of trainees. The data are informative to medical education leaders for the development of comprehensive TtP curricula.

National Trends and Dynamic Responses in the Canadian Radiation Oncology Workforce From 1990 to 2018.

PURPOSE: To report radiation oncology (RO) workforce and cancer incidence trends in Canada and explore the relationship between the two. METHODS AND MATERIALS: Canadian radiation oncologist, trainee, and cancer incidence data from 1990 to 2018 were collected from the following publicly accessible administrative and health information databases: Canadian Post-MD Education Registry (1990-2018), Canadian Medical Association Physician Data Centre (1994-2018), Canadian Institute for Health Information/Scott's Medical Database (1990-2017), Canadian Cancer Registry (1990-2017), and Statistics Canada (1990-2017). Descriptive statistics were used to summarize the data. RESULTS: The Canadian RO workforce grew from 240 radiation oncologists in 1990 to 567 in 2018, with the largest growth period from 2005 to 2015 adding 207 radiation oncologists. Regional analyses revealed steady or stepwise growth in all Canadian regions, except in Québec, where the number of radiation oncologists decreased from 86 in 1990 to 57 in 2003 before rising to 139 by 2018. Trainee totals were between 54 and 173 per year with 2 periods of growth (1990-1996 and 2001-2008) and regression (1996-2001 and 2008-2018), signifying trainee supply variability. Female proportions of the workforce and trainees, respectively, rose steadily from 18% to 38% and 28% to 50%, while the workforce proportion with non-Canadian medical degrees decreased from 40% to 26%. Radiation oncologists younger than 40 years increased from 70 to 171, whereas those age 60 years and older decreased from 85 in 1990 to 31 in 2002 and then increased to 108 in 2017. Annual cancer incidence rose steadily from 103,780 to 206,290 cases/year. The annual cancer incidence-to-provider ratio fluctuated (364-475:1) and trended lower with time, and proportional cancer incidence-to-provider ratios varied between 0.7:1 and 1.6:1 in Canada's regions before approaching 1:1. CONCLUSIONS: Our study demonstrates the challenges and successes of managing the Canadian radiation oncologist workforce. These data will inform policy makers and other stakeholders to ensure that the profession meets the current and future needs of Canadian cancer patients.

Taking Stock: The Canadian Association of Radiation Oncology 2017 Radiation Oncologist Workforce Study.

PURPOSE: To identify and report radiation oncologist (RO) workforce demographics, clinical workload trends, and equipment inventory in Canada. METHODS AND MATERIALS: The Canadian Association of Radiation Oncology (CARO) distributed an online survey to RO administrative leaders at 47 Canadian cancer centers providing radiation therapy services from June to December 2017. The survey queried RO staff demographics, clinical workload, and equipment inventory from 2014 to 2016. RESULTS: The response rate was 98% and represented 46 of 47 centers for analysis. In 2016, 510 ROs were in practice, with 98 ROs (19.2%) having <1.0 full-time equivalent (FTE) clinical work activities because of administration, research, or part-time employment. Most ROs worked full-time (92.0%), were affiliated with a university (77.5%), and worked in communities with a population >200,000 (84.9%). Approximately half (52.3%) were ≥46 years old. The male-to female ratio was 1.5:1 or higher in all regions of Canada except for Quebec, where there was no gender gap. Part-time employment was more common among female ROs (P < .01). Although FTE staff levels rose steadily between 2014 (456.3) and 2016 (475.8), an increase in patient workload resulted in a rise in the average annual consults per FTE-RO (from 257 to 267). Over a 2-year period, there were 63.5 FTE-recruitments and 44.0 FTE-departures (18.3 FTE-retirements; 25.7 FTE-migration) for a net gain of 19.5 RO-FTEs. An 8.4% increase in FTE staffing to 516 RO-FTEs in 2019 is anticipated, with 22 ROs expected to retire by 2019. There were 251 megavoltage linear accelerators across Canada, with most (39.8%) located in Ontario. Approximately one-fifth (20.7%) of these were older than 10 years and operating beyond the equipment's recommended life span. CONCLUSIONS: The Canadian RO workforce demonstrated incremental growth, but rising annual caseloads suggest that radiation therapy demand outpaced RO supply gains. Government funding is required to replace aging equipment in Canada.

Management of Medical Oncology Services in Canada: Redefined Workload With a Novel Supply-and-Demand Workforce Projection Model.

PURPOSE: We developed a workforce-planning model to predict Canadian medical oncologist (MO) supply and clinical demand during the next 10 years. MATERIALS AND METHODS: A forward calculation model was created to forecast the balance of MO supply and demand. MO supply was estimated by using Canadian Institute for Health Information, Canadian Medical Association, and Canadian Post-MD Education Registry data. Care demand was estimated by using data from Canadian Cancer Statistics and Alberta Cancer Registry. The Canadian Royal College MO Committee confirmed its face validity. RESULTS: The MO workforce is expected to grow from 541 staff in 2016 to 830 staff in 2026. During this period, new hires will increase from 39 to 56 per year, and departures will increase from 15 to 24 per year. Although cancer incidence rates will grow from 202,149 to 257,497, a projected increase in MO supply will mean fewer initial consultations, from an average of 168.5 consultations per MO in 2016 to 129.2 consultations per MO in 2026. The initiation of systemic therapy is projected to remain stable at 102.3 new systemic therapy starts per MO per year. CONCLUSION: We have developed a forward calculation MO workforce model that predicts a growing Canadian MO workforce and redefines MO workload dynamics. MO providers will increasingly support more follow-up care with the initiation of multiple lines of systemic therapy relative to the medical management of patients at the time of initial cancer diagnosis. Workload metrics, including follow-up and new therapy initiation rates, must be measured to appropriately to meet increasingly complex and growing care demands.

Does Motion Assessment With 4-Dimensional Computed Tomographic Imaging for Non-Small Cell Lung Cancer Radiotherapy Improve Target Volume Coverage?

INTRODUCTION: Modern radiotherapy with 4-dimensional computed tomographic (4D-CT) image acquisition for non-small cell lung cancer (NSCLC) captures respiratory-mediated tumor motion to provide more accurate target delineation. This study compares conventional 3-dimensional (3D) conformal radiotherapy (3DCRT) plans generated with standard helical free-breathing CT (FBCT) with plans generated on 4D-CT contoured volumes to determine whether target volume coverage is affected. MATERIALS AND METHODS: Fifteen patients with stage I to IV NSCLC were enrolled in the study. Free-breathing CT and 4D-CT data sets were acquired at the same simulation session and with the same immobilization. Gross tumor volume (GTV) for primary and/or nodal disease was contoured on FBCT (GTV_3D). The 3DCRT plans were obtained, and the patients were treated according to our institution's standard protocol using FBCT imaging. Gross tumor volume was contoured on 4D-CT for primary and/or nodal disease on all 10 respiratory phases and merged to create internal gross tumor volume (IGTV)_4D. Clinical target volume margin was 5 mm in both plans, whereas planning tumor volume (PTV) expansion was 1 cm axially and 1.5 cm superior/inferior for FBCT-based plans to incorporate setup errors and an estimate of respiratory-mediated tumor motion vs 8 mm isotropic margin for setup error only in all 4D-CT plans. The 3DCRT plans generated from the FBCT scan were copied on the 4D-CT data set with the same beam parameters. GTV_3D, IGTV_4D, PTV, and dose volume histogram from both data sets were analyzed and compared. Dice coefficient evaluated PTV similarity between FBCT and 4D-CT data sets. RESULTS: In total, 14 of the 15 patients were analyzed. One patient was excluded as there was no measurable GTV. Mean GTV_3D was 115.3 cm3 and mean IGTV_4D was 152.5 cm3 (P = .001). Mean PTV_3D was 530.0 cm3 and PTV_4D was 499.8 cm3 (P = .40). Both gross primary and nodal disease analyzed separately were larger on 4D compared with FBCT. D95 (95% isodose line) covered 98% of PTV_3D and 88% of PTV_4D (P = .003). Mean dice coefficient of PTV_3D and PTV_4D was 84%. Mean lung V20 was 24.0% for the 3D-based plans and 22.7% for the 4D-based plans (P = .057). Mean heart V40 was 12.1% for the 3D-based plans and 12.7% for the 4D-based plans (P = .53). Mean spinal cord Dmax was 2517 and 2435 cGy for 3D-based and 4D-based plans, respectively (P = .019). Mean esophageal dose was 1580 and 1435 cGy for 3D and 4D plans, respectively (P = .13). CONCLUSIONS: IGTV_4D was significantly larger than GTV_3D for both primary and nodal disease combined or separately. Mean PTV_3D was larger than PTV_4D, but the difference was not statistically significant. The PTV_4D coverage with 95% isodose line was inferior, indicating the importance of incorporating the true size and shape of the target volume. Relatively less dose was delivered to spinal cord and esophagus with plans based on 4D data set. Dice coefficient analysis for degree of similarity revealed that 16% of PTVs from both data sets did not overlap, indicating different anatomical positions of the PTV due to tumor/nodal motion during a respiratory cycle. All patients with lung cancer planned for radical radiotherapy should have 4D-CT simulation to ensure accurate coverage of the target volumes.

Clinical Implementation of a Model-Based In Vivo Dose Verification System for Stereotactic Body Radiation Therapy-Volumetric Modulated Arc Therapy Treatments Using the Electronic Portal Imaging Device.

PURPOSE: To report findings from an in vivo dosimetry program implemented for all stereotactic body radiation therapy patients over a 31-month period and discuss the value and challenges of utilizing in vivo electronic portal imaging device (EPID) dosimetry clinically. METHODS AND MATERIALS: From December 2013 to July 2016, 117 stereotactic body radiation therapy-volumetric modulated arc therapy patients (100 lung, 15 spine, and 2 liver) underwent 602 EPID-based in vivo dose verification events. A developed model-based dose reconstruction algorithm calculates the 3-dimensional dose distribution to the patient by back-projecting the primary fluence measured by the EPID during treatment. The EPID frame-averaging was optimized in June 2015. For each treatment, a 3%/3-mm γ comparison between our EPID-derived dose and the Eclipse AcurosXB-predicted dose to the planning target volume (PTV) and the ≥20% isodose volume were performed. Alert levels were defined as γ pass rates <85% (lung and liver) and <80% (spine). Investigations were carried out for all fractions exceeding the alert level and were classified as follows: EPID-related, algorithmic, patient setup, anatomic change, or unknown/unidentified errors. RESULTS: The percentages of fractions exceeding the alert levels were 22.6% for lung before frame-average optimization and 8.0% for lung, 20.0% for spine, and 10.0% for liver after frame-average optimization. Overall, mean (± standard deviation) planning target volume γ pass rates were 90.7% ± 9.2%, 87.0% ± 9.3%, and 91.2% ± 3.4% for the lung, spine, and liver patients, respectively. CONCLUSIONS: Results from the clinical implementation of our model-based in vivo dose verification method using on-treatment EPID images is reported. The method is demonstrated to be valuable for routine clinical use for verifying delivered dose as well as for detecting errors.

Prospective swallowing outcomes after IMRT for oropharyngeal cancer: Dosimetric correlations in a population-based cohort.

OBJECTIVES: To identify dose constraints to preserve swallowing after head and neck (H&N) radiotherapy using prospectively collected functional outcomes. MATERIALS AND METHODS: Stage III-IV oropharyngeal cancer patients were prospectively evaluated using the Royal Brisbane Hospital Outcome Measure for Swallowing and Performance Status Scale for H&N Cancer Patients at pre-treatment and 3, 6, 12, and 24months after intensity-modulated radiotherapy. Dosimetric parameters were correlated with swallowing function. RESULTS: Ninety-six patients were evaluated with median follow-up of 14.1months (interquartile range 9.9-26.3). Six patients (8.3%) remained feeding tube (FT) dependent at 12months. At 2years, 32.6% tolerated a normal diet without restrictions. Mean doses of 55Gy to supraglottic larynx, 44Gy to glottic larynx, 48Gy to cricopharyngeus, and 44Gy to esophageal inlet were associated with >25% risk of FT dependence at 6months. CONCLUSION: Higher mean doses to the larynx and pharyngo-esophageal junction were associated with longer duration of FT dependence and dietary restrictions.

Delayed Workforce Entry and High Emigration Rates for Recent Canadian Radiation Oncology Graduates.

PURPOSE: To determine the employment status and location of recent Canadian radiation oncology (RO) graduates and to identify current workforce entry trends. METHODS AND MATERIALS: A fill-in-the-blank spreadsheet was distributed to all RO program directors in December 2013 and June 2014, requesting the employment status and location of their graduates over the last 3 years. Visa trainee graduates were excluded. RESULTS: Response rate from program directors was 100% for both survey administrations. Of 101 graduates identified, 99 (98%) had known employment status and location. In the December survey, 5 2013 graduates (16%), 17 2012 graduates (59%), and 18 2011 graduates (75%) had permanent staff employment. Six months later, 5 2014 graduates (29%), 15 2013 graduates (48%), 24 2012 graduates (83%), and 21 2011 graduates (88%) had secured staff positions. Fellowships and temporary locums were common for those without staff employment. The proportion of graduates with staff positions abroad increased from 22% to 26% 6 months later. CONCLUSIONS: Workforce entry for most RO graduates was delayed but showed steady improvement with longer time after graduation. High emigration rates for jobs abroad signify domestic employment challenges for newly certified, Canadian-trained radiation oncologists. Coordination on a national level is required to address and regulate radiation oncologist supply and demand disequilibrium in Canada.

Liver toxicity prediction with stereotactic body radiation therapy: The impact of accounting for fraction size.

PURPOSE: Current liver SBRT protocols rely on the calculation of "effective volume" without accounting for the biologic effect of fraction size to estimate the risk of liver toxicity, which subsequently defines tumor prescription doses. This study compared effective volume and liver toxicity predictions with and without correction for fraction size. METHODS AND MATERIALS: The effective volume was determined for 18 liver SBRT plans with and without biologic normalization using the linear quadratic formula. Lyman-Kutcher-Burman normal tissue complication probability models estimated the risk of liver toxicity. Effective volumes and corresponding toxicity predictions were compared with and without biologic normalization. RESULTS: Accounting for the biologic difference of larger fraction size reduced the effective volume in all treatment plans compared with the unadjusted effective volume (median effective volume 0.21 vs 0.32). The lower effective volume with biologic normalization substantially reduced the estimated risk of liver toxicity (average risk of toxicity 32% vs 4.5%). CONCLUSIONS: This study demonstrates that accounting for the biologic effect of fraction size with effective volume significantly decreases predicted hepatic toxicity, which suggests that the risk of liver toxicity may be overestimated in clinical practice if biologic normalization is omitted. The effective volume toxicity model has proven safe in prospective clinical trials, though safe dose escalation with liver SBRT may be feasible.

Specific mutations in transmembrane helix 8 of human concentrative Na+/nucleoside cotransporter hCNT1 affect permeant selectivity and cation coupling.

The Na+/nucleoside cotransporters hCNT1 (650 residues) and hCNT2 (658 residues) are 72% identical in amino acid sequence and contain 13 putative transmembrane helices (TMs). Both transport uridine and adenosine but are otherwise selective for pyrimidine (system cit) and purine (system cif) nucleosides, respectively. Previously, we used site-directed mutagenesis and functional expression in Xenopus oocytes to identify two pairs of adjacent residues in TMs 7 and 8 of hCNT1 (Ser319-Gln320 and Ser353-Leu354) that, when converted to the corresponding residues in hCNT2 (Gly-Met and Thr-Val, respectively), changed the permeant selectivity of the transporter from cit to cif. We now report an investigation of the effects of corresponding mutations in TM 8 alone and demonstrate unique S353T- and L354V-induced changes in nucleoside specificity and cation coupling, respectively. hCNT1 mutation S353T produced a profound decrease in cytidine transport efficiency (Vmax/Km ratio) and, in combination with L354V (S353T/L354V), resulted in a novel uridine-preferring transport phenotype. In addition, the L354V mutation markedly increased the apparent affinity of hCNT1 for Na+ and Li+. Both hCNT1 TM 8 residues exhibited uridine-protectable inhibition by p-chloromercuribenzene sulfonate when converted to Cys, suggesting that they occupy positions within or closely adjacent to a common cation/nucleoside translocation pore.